KR19990022224A - On-site mixing systems and methods for ultra-pure chemicals for semiconductor processes - Google Patents

Abstract

Systems and methods for mixing and / or diluting ultra-pure fluids such as liquid acids in semiconductor processes. The system includes first and second chemical dispensers adapted to respectively receive first and second fluids to be mixed; A process connection between a first distributor and a second distributor for mixing the first and second fluids to flow through the first and second chemical distributors and form a mixed fluid, To further flow the mixed fluid through the desired region; Is provided in an area sufficient to transmit ultrasonic waves through the mixed fluid and indirectly measures the rate defined by the amount of the first chemical in the mixed fluid versus the amount of the second chemical by measuring the speed of the sound waves through the mixed fluid And an ultrasonic radiation device.

Description

On-site mixing system and method of ultra-pure chemical for semiconductor process

The present invention relates to conventional semiconductor processes, and more particularly to a method for mixing ultra-pure liquid reagents with high accuracy.

On-site Super Refinement Process

The present invention relates to a method for producing an ultra-pure liquid reagent in an on-site system installed at a semiconductor wafer production site, wherein the ultra pure liquid reagent comprises steps of distilling ammonia vapor from a liquid ammonia reservoir and drawing, And scrubbing the steam filtered with purified water (preferably ultra-pure deionized water equilibrated with an ammonia stream). The present invention makes it possible to convert commercial ammonia into high purity ammonia which is sufficient for high-precision production without the use of conventional distillation tubes. Ammonia vapors extracted from the feed reservoir act as a single stage distillation process and operate as a single stage distillation process to remove alkaline and alkaline earth metal oxides, carbonates and hydrides, transition metal halides and hydrides, and nonvolatile and hydrocarbons such as high boiling hydrocarbons and halogenated carbons High boiling point impurities are removed. Volatile impurities of reactivity that can be found in commercial ammonia, such as certain transition metal halides, Group III metal hydrides and halides, Group IV hydrides and halides, and halogens, which previously were believed to be removed only by distillation, It has been found that it can be removed by a super refining process to a degree suitable for high-precision operation. This is a very surprising finding because the cleaning technique is commonly used to remove large scale impurities rather than fine scale. Such systems are described in co-pending U.S. Patent Application Serial No. 08 / 179,001, filed July 1, 1994, and in pending virtual patents 08 / 499,425, 08 / 499,414, and 08 / 499,413, Lt; / RTI >

The present invention is also a development of an on-site purification system for hydrogen peroxide. A detailed description of such a system is provided in copending U.S. Patent Application Serial No. 08 / 499,427, filed Jul. 7, 1995, Lt; / RTI >

BACKGROUND ART Wet versus dry process

One of the long-used technological implementations in semiconductor processes is the shift (and attempt to change) between dry and wet processes. In the dry process, only the gaseous or plasma phase reactant comes into contact with the wafer. In wet processes, various liquid reagents are used for etching silicon dioxide or removing native oxide layers, removing organic or organic contaminants, removing metal or organic contaminants, silicon nitride etch, silicon etch, and the like.

Plasma etching has many attractive properties, but is unsuitable for cleaning. Because there is no chemical treatment available to remove some of the most undesirable impurities such as gold. Therefore, the cleaning process is essential to current semiconductor processes and will continue to exist in the future.

Plasma etching is performed using a suitable photoresist and is not immediately followed by a high temperature step. Instead of the strip being stripped, it is necessary to perform cleaning.

Materials removed by cleaning include photoresist residues (organic polymers), sodium, alkaline earths (e.g., calcium or magnesium), and heavy metals (e.g., gold). Since the majority do not form volatile halides, plasma etching can not remove them. Therefore, it is necessary to clean using a wet chemical treatment.

As a result, the purity of the chemical in the plasma etching process is not critical, since these steps are always followed by a cleaning step before the high temperature treatment step is performed, and the cleaning step is carried out before the high temperature treatment step To remove dangerous contaminants. However, the impingement rate at the semiconductor surface is more than one million times higher than the impingement rate at plasma etching, and the purity of the liquid chemical becomes more important since the liquid washing step is immediately followed by the high temperature treatment step.

However, the wet process has a serious defect called so-called ionic contaminants. Integrated circuit structures use only a few dopants (boron, arsenic, phosphorus, and sometimes antimony) to form the desired p-type and n-type doped regions. However, many other types of dopants are electrically active dopants and are highly undesirable contaminants. Many such contaminants may have adverse effects, such as increased bond leakage, at concentrations far below 10 ¹³ cm ^-3 . In addition, some of the less desirable contaminants are separated into an aqueous solution in which the equilibrium concentration of the contaminants is higher in the silicon than in the solution, and silicon in which the silicon contacts. In addition, some of the less desirable contaminants have a very high diffusion coefficient, so that when such dopants are injected into any portion of the silicon wafer, they can diffuse through a location containing the junction that causes leakage .

Therefore, it is desirable that all liquid solutions used in semiconductor wafers have very low levels of total metal ions. The concentration of all metals to be combined is preferably 300 ppt (1 / tenth) or less, preferably 10 ppt or less for any metal, and more preferably less than 300 ppt. In addition, contaminants can be controlled by both anions and cations. That is, some anions, such as alloy ions, can have the adverse effect of reducing the mobile metal atoms or ions in the silicon lattice.

The anteroposterior facility typically has an on-site purification system to produce high purity water (expressed as DI water, i.e., DI). However, it is more difficult to obtain process chemicals of the required purity.

BACKGROUND ART:

The top priority in the semiconductor processing industry is precise mixing of chemicals. Changes in the concentration of the reagent are due to uncertainties in the rate of corrosion (sometimes selective), which may cause subsequent process changes. Since changes due to various causes are accumulated, process changes are not preferable at all.

Many ultra-pure chemicals are required as diluents rather than just one dilution. For example, several different concentrations of HF are commonly used. However, the transportation cost per unit volume of high purity chemical is high, so that the cost of transporting all necessary concentrations of chemicals to the manufacturing site can be extremely high. In particular, it is even more uneconomical for very dilute acidic solutions which are used occasionally.

Some semiconductor manufacturers use on-site mixing methods in their manufacturing processes to produce some dilute chemicals, such as hydrofluoric acid. This on-site mixing method is profitable because it reduces the cost by:

- As the concentrated distillate is transported, no additional costs of transporting water to dilute the solution occur;

- the concentration of only one or a significantly reduced number of chemicals than normal is tested and handled in lieu of some dilution chemicals;

- Real-time concentration adjustment is possible since the time required for transport and treatment is not required to make concentration adjustments.

However, it is necessary to strongly suppress the extremely simple operation of an ordinary precision chemical system.

Background: Ultrapure mixing using charged cells

In its present form for on-site dispensing equipment, it is known to use loading cells to control the amount of chemicals being dispensed. However,

- unpredictable forces exerted by pipe connections attached to the metered mixing vessel;

- a calibration program to compensate for the experimental equipment and the amount of change in content needed to analyze the chemical content to be injected;

A scale resolution inaccuracy that exists at a large dilution rate;

- There is a restriction that expensive electronic equipment, which is normally required, is exposed to corrosive chemical environments and therefore must be easy to eradicate or to use noncorrosive equipment if available and practicable.

Other known alternatives employ a volumetric method as disclosed in U.S. Patent Nos. 5,148,945, 5,330,072, 5,370,269, and 5,417,346 to Applied Chemical Solutions, Hollister, Calif. However, although these systems can provide increased resolution at high dilution rates, they are not available for rate changes.

Therefore, there is a desperate need for effective low-cost equipment that mixes chemicals on-site in the semiconductor industry and other industries using chemical mixtures.

Innovative systems and methods for ultra-pure liquid mixing

This application describes a new method of on-site ultra-pure liquid mixing in semiconductor production facilities. To provide precise control while maintaining very tight control over the contaminants, multiple component mixing is done using continuous additives.

Such a system is preferably provided with a closed loop automatic control system in which an electrical signal indicative of the sensed velocity or the calculated density is supplied to the outflow controller and the process connection upstream of the point where the first and second fluids are intermixed And fed back to the outlet control valve (feedback control system). Optionally or in conjunction, a feedforward control algorithm may be used. That is, the system can use a means of sensing the components of the time-varying source chemistry to provide such sensing data to the control structure that controls downstream outflow.

The good system is a system in which three or more chemicals are sequentially mixed, that is, the first and second chemicals are first mixed to form a first mixed fluid, and the first mixed fluid is mixed with a third fluid chemical 2 mixed fluid to form an n-1 mixed fluid, wherein n is the number of fluids to be mixed.

Another aspect of the present invention is a method of mixing two or more superfluid fluids,

Providing at least a first fluid and a second fluid to be mixed;

Flowing the fluid through a means for forming the mixed ultra pure fluid;

Providing ultrasound through the mixed fluid;

Measuring the velocity of the waveform passing through the mixed fluid thereby indicating the density of the mixed ultra-pure fluid and indirectly measuring the ratio of the amount of the first fluid to the amount of the second fluid of the mixed fluid .

An embodiment of a good system and method includes a computer having means for monitoring and controlling a mix of chemicals in real time by receiving a signal from a sound wave concentration monitor and comparing the received signal to a target rate, .

As a result,

The content of each chemical agent can be analyzed with the system, and automatic compensation for the degree of change can be programmed into the mixing controller;

Charging cell problems are prevented, and accuracy is improved;

The advantage is that a high resolution is provided by an ultrasonic system providing a mixing accuracy of 1/200 or more.

Further features and advantages of the present invention will be presented in accordance with the detailed description of the invention which will be described hereinafter.

The disclosed invention will be described with reference to the accompanying drawings, which are incorporated herein by reference and which represent important sample embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1A is a schematic process flow diagram illustrating a system according to the present invention in a reduced scale.

Figures 2A-2D are graphs illustrating velocity versus concentration for a particular fluid mix discussed in an embodiment in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an engineering flow diagram of one example of a unit for producing ultra-pure ammonia.

Figure 2 is a block diagram of a semiconductor manufacturing line in which the ammonia purification step of Figure 1 can be integrated.

FIG. 3A is a schematic diagram of a process flow in a generation unit producing ultra-pure ammonia into a hydrofluoric acid to produce buffered HF, and FIGS. 3B1 to 3B3 are detailed PIDs of a sample implementation of the process flow of FIG. 3A;

4 depicts an on-site HF purifier according to an innovative sample embodiment disclosed.

5 shows the effect on the sound velocity of a mixture of HF, HNO ₃ , and HA _C when HNO ₃ and HA _C are added sequentially to HF of any volume with known concentration and velocity. First, HNO ₃ is added in a specific volume ratio and HA _C is added in the final specific volume ratio. The final volume ratio of the test solution 6: 1: 5 and 3: 1: 2 was _{(HF: HNO 3: HA C} ). It was observed that the sonic speed of the mixture was increased by addition of HNO ₃ and decreased by addition of HA _C.

Figure 6 shows the effect of the sound speed of the concentration of HNO ₃ in the time the concentration of the HF is added in three separate samples. The sound velocity is maximum when the ratio of HNO ₃ to HF is maximum.

Figure 7 shows the effect of known HF concentration on sonic speed when the nitric acid and acetic acid are added sequentially. The sonic velocity was increased when nitric acid was added, but decreased when acetic acid was added.

Numerous innovative features of the present application will be described (by way of example and not of limitation) with reference to the preferred embodiments presented.

1A is a schematic process flow diagram of a preferred system embodiment of the present invention. The main components of the system are the mixing tank 2, the finished product storage tank 4, and the chemical distributor 6. The first, second, and third chemicals C1, C2, and C3 flow into the system through the conduits 8, 10, and 12, respectively. The deionized water will flow through the conduit 14. The conduits 8, 10, 12, and 14 are encountered in the mixing tank 2, as shown, even though they use different pipe arrangements.

It is preferable that the two pumps 16, 18 are installed around the mixing tank 2. The pumps 16, 18 are preferably pneumatically operated using clean air supplied by the conduit 20. When the pump 18 operates as a drain pump, the pump 16 operates as a chemical mixture delivery pump that delivers the chemical mixture to the finished product storage tank 4. The chemical mixture delivery pump 16 draws the mixture from the conduit 24 and discharges the mixture introduced from the pump 16 through the outlet conduit 26 to the tank 4.

The level maintained in the mixing tank 2, i.e., the control unit 22, by a known method and apparatus, such as a level sensing technique, compares the actually measured level with the programmed set-point level. If the measurement level is too low, the control unit 22 signals the control valve 23 to send more chemicals C1 to the mixing tank 2. It will be appreciated by those skilled in the art that other variations may be possible to control the level.

An important feature of the present invention resides in the provision of the sound wave synthesis module 28, represented herein as an SCM. The SCM 28 measures the velocity of the sound waves or pulses passing through the chemical mixture passing through the exhaust conduit 26. The velocity (sonic velocity) of the sonic pulse passing through the chemical mixture is directly related to the concentration of Cl in C2, or, more suitably, to the volume ratio of C1 to C2 in the chemical mixture of C1 and C2. If the speed is too low or too high, depending on the set or target ratio, the SCM 28 may be programmed to one of several of the circulation control valves, such as the control valves 29 and 31, Send the appropriate electronic signal (the signal is sent to only one of the control valves at a time, so the chemical addition to the mixture is sequential). This feedback control logic may be modified, for example, by a feedforward master control loop having purity or concentration of chemicals C1, C2, and the like, and upstream sensing components such as control valves 23, 29, 31 and the like. The actual purity or concentration may be compared to the set purity or concentration and the appropriate signaling is sent to the control valve 23, 29, or 31 to compensate for the purity change. Of course, caution should be exercised when using sensing elements that do not themselves prevent unnecessary contamination of mixed chemicals.

Commercially available SCMs, which are preferably used in the systems and methods of the present invention, are known as MODEL 88, 88 SCM, which is a product of MESA Laboratories, Inc., of the Nusonis Division of Wheat Ridge, Colorado. As specified in these units in the Operating Manual (incorporated herein by reference), the concentration output is a calculation derived from a process model that takes into account the influence of concentration and temperature, and the pressure on the velocity in the fluid . Concentrations can be expressed in various units such as weight percent, density / specific gravity, ° Brix, or ° Baume.

A good SCM has two main assemblies: a transmitter and a transducer. The transmitter is typically installed within about 25 to 100 feet of the transducer. The transducer is a wetted element of the SCM. The transducer is installed within the process conduit, as is the conduit 26 shown in FIG. The transducers can also be installed in the sampling loop. A preferred transducer has both a speed transducer and a temperature transducer, and more preferably is integrated into the same transducer body to prevent the elastomeric seal from being torn under high pressure, temperature or in a corrosive environment. Another preferred transducer is in the form of a spool, with a spool having a diameter approximately equal to that of the conduit through which the chemical mixture passes. The spool has a receiving transducer, a flush with five walls, and an individually mounted temperature transducer, which are placed facing each other with their respective transits. Two types of transducers can be used for the SCM known as MESA LABORATORIES 'product registered trademark MODEL 88.

As mentioned earlier, pressure transducers can be integrated into the SCM used, but pressure transducers are rarely needed because only 0.01 meter / second / psi affects sound velocity.

The transmitter and transducer operate as described in the MESA manual incorporated herein by reference.

Another important feature of the present invention is the provision of level controllers (32, 34, 36, 38) on the finished product storage tank (4). The level controller guarantees batch mixing and input supply, which can be done on demand, without dangerous overflow or discharge.

In the preferred embodiment using the systems and methods of the present invention, first, the chemical liquid to be mixed is selected. The first chemical is produced in the mixing tank at a known dilution rate. The amount of the first chemical is not particularly critical, but the overfilling of the mixing tank should be avoided. A second chemical that is mixed with the first chemical is selected and produced in the mixing tank. The mixing tank includes mixing means sufficient to intimately mix the medicaments, such as, for example, a stirrer, a shield, a stopper, and the like. The outflow from the mixing tank is initiated through a conduit leading to the finished product storage tank. A sonic concentration monitor (SCM) is provided in the conduit that transmits the sonic signal through the fluid mixture. That is, the speed of the sonic signal is measured and compared to the set or target mixture, and one or more valves are actuated to adjust the flow of either chemical or deionized water to produce the desired ratio of chemicals C1 and C2 A signal is generated. The third, fourth, and nth chemicals are added to the mixing tank in the same sequential manner to produce the second, third, and n-1 mixture.

The present invention will be better understood with reference to the following examples, in which all ratios and percentages are by weight unless otherwise indicated.

Example 1

In this example, the on-site mixing unit was used to mix hydrofluoric acid (HF), nitric acid (HNO ₃ ), and acetic acid (CH ₃ COOH or HA _C ) at various volume ratios. The mixing process was carried out in the following order.

1) 49% HF was added to the empty mixing tank,

2) HNO ₃ is added at a specific volume ratio,

3) Finally add HA _C to the final volume ratio.

The most preferred method of performing component measurements and control is to use the Mesa Labs Model 88 Sonic Concentration Monitor (SCM). Therefore, a preliminary check has been made to confirm useful changes in sonic speed due to sequential addition of each of the above components. Of course, the additional measurement and mixing steps used for sensitivity verification are not part of the normal product.

Advance confirmation procedure

This experiment was performed in accordance with Section 4.3 of the Model 88 SCM Operating Manual. In this verification procedure, a magnetic stirrer was used to minimize temperature changes (typically magnetic stirrers not used in the ultra pure product plant). The experimental method was as follows.

1) 49% HF (at a known rate) was added

2) Add HNO ₃ (at target volume ratio of -5%) and measure the velocity

3) Add HNO ₃ to target volume ratio and measure velocity

4) Add HNO ₃ (target volume ratio + 5%) and measure the velocity

5) Add HA _C (to the target volume ratio of -5%) and measure the velocity

6) Add HA _C as target volume ratio and measure velocity

7) Add HA _C (target volume ratio + 5%) and measure the velocity

A 50.0 ml standard burette was used to measure the constituent content. Two samples of HG: HNO ₃ : HA _C solution, 6: 1: 5 and 3: 1: 2, were selected for this test. The test identified a useful rate / concentration slope at the sample endpoint.

In the first test, the volume ratio of HG: HNO ₃ : HA _C was approximately 6: 1: 5, and the volume of the second test was approximately 3: 1: 2. The concentration (wt%) of the three acids used was 49% HF; 70% nitric acid; Acetic acid was 99.5%.

In each case, sonic velocity was increased by nitric acid addition and decreased by acetic acid addition.

Pre-confirmation results using 6: 1: 5 mixture

The results for the 6: 1: 5 mixture are as follows.

Start Addition Cum △ V _acou Temp ℃ 110 ml HF 1327.76 22.20 + 10㎖ HNO ₃ 10 nit 1338.49 22.45 + 7.3㎖ HNO ₃ 17.3 nits 1345.60 22.58 HNO ₃ + 1㎖ 18.3 nit 1346.21 22.61 + 0.9㎖ HNO ₃ 19.2 nit 1346.81 22.65

Table 1 shows the first stage of a tightly controlled semiconductor evaluation chemical mix. Figure 2A is derived from such data and is a diagram showing the relationship between sound velocity and concentration. As this data indicates, sonic velocity provides a good one-dimensional measurement of the concentration for this range of mixtures.

The product thus produced is used in the second mixing stage, and the third component is mixed.

Start Addition Cum △ V _acou Temp ℃ 100㎖ HF + HNO ₃ 1346.81 + 30 ml HAc 49.2 1316.53 21.30 + 10 ml HAc 59.2 1309.09 21.28 + 28 ml HAc 87.1 1293.95 21.00 + 3.6 ml HAc 90.7 1292.02 21.15 + 3.5 ml HAc 94.2 1290.22 21.2

FIG. 2B is a diagram derived from the data in Table 2 and showing the relationship between sound velocity and concentration. FIG. As this data indicates, sonic speed provides a good one-dimensional measurement concentration for this range of mixtures. Therefore, a combination of two sequential mixing steps allows the concentration of the three component mixtures to be accurately measured with a one-dimensional sensor (sonic sensing).

Pre-confirmation results using 3: 1: 2 mixture

The results of preliminary confirmation using 3: 1: 2 mixture are as follows.

Start Addition Cum △ V _acou Temp ℃ 120 ml HF 1329.69 22.5 + 30㎖ HNO ₃ 30 nit 1355.39 27.9 + 8㎖ HNO ₃ 38 1361.08 22.95 + 2㎖ HNO ₃ 40 1362.46 22.93 + 2㎖ HNO ₃ 42 1363.84 22.93

Table 3 shows the first stage of a tightly controlled semiconductor evaluation chemical mix. Figure 2A is derived from such data and is a diagram showing the relationship between sound velocity and concentration. As this data indicates, sonic velocity provides a good one-dimensional measurement of the concentration for this range of mixtures.

The product thus produced was used in the second mixing stage, and the third component was mixed.

Start Addition Cum △ V _acou Temp ℃ 100㎖ _3: 1HF: HNO 3 + 30 ml HAc 72 1320.09 21.1 + 18 ml HAc 89.6 1315.18 20.88 + 2.5 ml HAc 92 1313.31 20.95 + 2.5 ml HAc 94.6 1311.6 21

2D is a diagram derived from the data in Table 4 and illustrating the relationship between sound velocity and concentration. As this data indicates, sonic speed provides a good one-dimensional measurement concentration for this range of mixtures. Therefore, a combination of two sequential mixing steps allows the concentration of the three component mixtures to be accurately measured with a one-dimensional sensor (sonic sensing).

Sensitivity of measurement

The slope of each plot for the concentration range considered is given in the following table. Each slope is significantly larger than the slope required in the experiment by 0.1m / s repetition of the Model 88.

inclination

When nitric acid is added to the 6: 1: 5 product m1 = 1.165 (m / s / 0.1-part)

6: 1: 5 When acetic acid is added to the product... M2 = -3.655 (m / s / 0.1-part)

When nitric acid is added to the 3: 1: 2 product m3 = 2.76 (m / s / 0.1-part)

When acetic acid is added to the 3: 1: 2 product m4 = -3.58 (m / s / 0.1-part)

Although direct thermal measurements on the reaction data can not be used, the observed maximum temperature rise was approximately 0.4 ° C. The heat of reaction is not considered to be an important index. (Note: Typical oxidation system temperature coefficients provided by Mass Labs for Model 88 are 2 to 4 m / s per degree Celsius). Although the heat of reaction is small, the temperature control capability in the installed unit is required.

Example 2

A second three-component system useful for semiconductor processing is a dilution of various buffered hydrofluoric acids. In this system, the constituents are aqueous HF, NH ₄ F, and ultra-pure (DI) water.

In this kind of embodiment, aqueous HF and aqueous ammonium fluoride are incorporated herein by reference and can be used to produce on-site semiconductor production using systems and methods such as those disclosed in < RTI ID = 0.0 > And is preferably generated in the facility. In this embodiment, first an ultra-pure gaseous body HF is produced, and then a super-hydrophobic aqueous HF is produced (by sonic speed sensing, or at a concentration measured by a conductivity measurement on a dilute solution). The ultra-pure gaseous ammonia is boiled in the ultra-pure aqueous HF under the control of the one-dimensional sensing output to generate the HF buffered at the desired strength, after being generated individually. Therefore, again two sequential combining steps provide precise control of the 3-component mixture. The individual steps of this process will be described in more detail. It should be noted that all of these steps were performed on an on-site semiconductor production facility.

Purification of NH ₃

According to the present invention, the ammonia vapor is first extracted at the vaporization location in the liquid ammonia supply reservoir. Extraction vapors of this type operate in a single stage distillation process, forming a particular solid in the liquid state, leaving a high boiling impurity. The feed reservoir may be a conventional feed tank or other reservoir suitable for receiving ammonia, which is in the form of an anhydrous or aqueous solution. The reservoir can be maintained above atmospheric pressure, if it is desired to shed more ammonia into the system or atmospheric pressure. The temperature is preferably in the range of from about 10 캜 to about 50 캜, preferably from about 15 캜 to about 35 캜, and most preferably from about 20 캜 to about 25 캜, as the reservoir is preferably thermally controlled.

The impurities removed as a result of the extraction of ammonia from the vapor phase are the aminated versions of these metals formed as a result of contact with ammonia as well as Group I and Group II metals of the Periodic Table. The material to be removed also includes oxides or carbides of such metals, as well as hydroxides such as beryllium hydroxide and magnesium hydroxide; Group III elements and their oxides, as well as ammonium by-products of hydroxides and halides of such elements; Transition metal hydroxides; And halogenated carbons such as heavier hydrocarbons and pump oils.

Ammonia extracted from the reservoir passes through the filtration unit to remove any solids associated with the vapor. Membranes capable of commercialization with microfiltration devices and ultra filtration devices can be used. The class and type of filter are selected as needed. In the presently preferred embodiment, after a 0.1 micron filter, a gross filter is used in front of the ion purifier, and there is no filter after the ion purifier.

The filtered steam is passed through a scrubber and rinsed with high pH purified (preferably deionized) water. It is preferable that the high pH water is an aqueous ammonia solution whose concentration is increased until it is saturated by recycling through a scrubber. The scrubber can be operated like a conventional scrubbing distillation tube of the reverse current type. Although the operating temperature is not critical, the distillation column is preferably operated at a temperature ranging from about 10 캜 to about 50 캜, and more preferably from about 15 캜 to about 35 캜. Likewise, although the operating pressure is not critical, good operation is performed at a pressure of about atmospheric pressure and a pressure of about 30 psi or more of atmospheric pressure. The distillation tube usually accommodates a conventional distillation tube that packs to provide a high degree of contact between the liquid and the gaseous body, and it is preferable that the distillation tube is a fogging section.

In a preferred embodiment of the present invention, the distillation tube has a packing height of approximately 3 feet (0.9 m) and an inner diameter of approximately 7 inches (18 cm) to obtain a packing volume of 0.84 cubic feet (24 l) (0.075 kPa) and a recirculation flow of 5 gallons per minute (.32 l / s) per minute at nominal or 20% flow of about 2.5 gallons per minute (0.16 l / s) A gas inlet, and a liquid inlet on the packing, below the fog removal section. The distillation tube of the present specification is a packing material having a nominal dimension of distillation tube diameter of 1/8 or less. The de-fogging section of the distillation tube has the same or more compact packing than the prior art, while the structure is conventional. The description and dimensions of this paragraph are to be regarded as illustrative only and each parameter of the system may be varied.

In normal operation, startup first saturates the deionized water with ammonia to form the solution used as the medium to initiate cleaning. During operation of the scrubber, a small amount of liquid in the sump of the distillation column is periodically drained to remove accumulated impurities.

With an impurity which is removed by the cleaner is silane (SiH ₄₎ and arsine (AsH _3); Halides and hydroxides of phosphorus; Arsenic and antimony; Common transition metal halides; And reactive volatiles such as Group III and Group IV metal halides and hydroxides.

The units described so far can be operated in a continuous or semi-continuous arrangement manner, and continuous or semi-continuous operation is preferred. The volumetric throughput of the ammonia refining system is not critical and can vary widely. Most of the operations of the present invention are for use, but the outflow rate of ammonia through the system will be from about 200 cc / h to several thousand t / h.

Ammonia remaining in the scrubber can optionally be further purified prior to use depending on the particular type of manufacturing process in which the ammonia is to be purified. When ammonia is used in the chemical vapor deposition process, it is advantageous for the system to include a dehydration unit and a distillation unit. Fraction distillation tubes may be operated in a continuous or semi-continuous manner. In batch operation, typical operating pressures may be 300 pounds per square inch (2.068 kPa) with a batch size of 100 pounds. The distillation tube in this example had a diameter of 8 inches (20 cm), a height of 72 inches (183 cm), a steam velocity of 0.00221 feet (0.00067 m / s) per second, a 1.5 inch ), And 48 copper plates. In this embodiment, the size of the boiler was about 18 inches (47.5 cm) in diameter and 27 inches (68.6 cm) in length and had a backflow rate of 0.5, with recirculated cooling water flowing at 60 ° F (15.6 ° C) F (32.2 占 폚). Once again, this is just an example. Fractional distillation tubes can greatly change the structure and selective parameters can be used.

Depending on the application, purified ammonia, with or without distillation, can be used as a purified gas or aqueous solution, in which case the purified ammonia is dissolved in purified water, preferably deionized water. Mixing ratios and mixing means are the same as in the prior art.

A flowchart depicting one embodiment of an ammonia purification unit in accordance with the present invention is shown in FIG. The liquid ammonia was stored in the reservoir (11). The ammonia gas 12 is extracted from the gas space in the reservoir, passed through the shutoff valve 13, and then through the filter 14. The purified ammonia base 15, whose flow is controlled by the pressure regulator 16, is sent to the washing distillation tube 17 which contains the packed section 18 and the fading pad 19. When the ammonia gas moves upward, the saturated aqueous ammonia 20 flows out downward, the liquid is circulated by the circulation pump 21, and the liquid level is controlled by the level sensor 22. The wastes (23) remaining at the bottom of the scrubber from the liquid are discharged periodically. The deionized water 24 is maintained at a pressure raised by the pump 25 and supplied to the washer 17. The cleaned ammonia 26 has three routes:

1) Fractionation distillation column (27) in which ammonia is further purified. The distilled ammonia (28) product is sent to the destination.

2) a dissolving unit 29 that forms an aqueous solution 31 when ammonia is combined with deionized water 30 and sent to a destination. Ammonia may be withdrawn from the aqueous solution sent to multiple destinations of the same production plant and sent to individual lines for collection of a plurality of destination production operations for storage tanks.

3) to one of the transport lines 32 carrying the gaseous form of ammonia to the destination.

The second and third routes that do not utilize the fractionation line 27 are suitable for producing ammonia of less than 100 ppt (parts per trillion) of any metallic impurity. However, it is preferable that the fractionation distillation pipe 27 is included in the special use. Embodiments use a furnace using ammonia or chemical vapor deposition (CVD). When ammonia is used for CVD, for example, the fractionation tube 27 removes non-condensable materials, such as oxygen and nitrogen, that can interfere with CVD. Further, the ammonia remaining in the scrubber 17 is saturated with water, and the dehydration unit is optionally integrated between the scrubber 17 and the fractionation distillation tube 20 in the system according to the characteristics and efficiency of the fractionation distillation column .

In the above methods, the product stream, which is gaseous ammonia or an aqueous solution, can be divided into two or more branch streams, each sent to a different location, and the purification unit is capable of separating the purified ammonia into a plurality of locations Simultaneously.

Purification of HF

Figure 4 illustrates an on-site HF purification process in accordance with the disclosed sample embodiment.

The reaction starting material is preferably high purity 49% HF, which is essentially free of arsenic. These low arsenic materials are available from Allide Chemical.

The HF treatment process comprises an evaporation (and arsenic removal) stage, a fractional distillation column to remove most other impurities, an ionic purifier distillation column to remove contaminants not removed by the fractional distillation column, and an HF feeder (HFS).

Alternatively, the batch process arsenic removal step may be combined with the evaporation step. In this process, arsenic is removed by addition of a cation source, such as KMnO ₄ or (NH ₄ ) ₂ S ₂ O ₈ , and KHF ₂ to form K ₂ AsF ₇ salt, And stored in the evaporator. This process will be a batch process since the reaction is slow and sufficient time is allowed to complete the reaction before the distillation is performed. This process requires about 1 hour of contact time at the nominal temperature. To achieve a complete reaction in a continuous process, high temperature and high pressure (undesirable for safety) or very large vessel and pipe connections are required. In this process, HF is introduced into the batch process evaporation vessel and treated with an oxidizing agent while stirring for a suitable reaction time.

HF removes the bulk of the metallic impurities after distillation in countercurrent distillation tubes. The elements that decrease significantly at this stage are:

Group 1 (I) Na

Group 2 (II) Ca, Sr, Ba

Group 3-12 (IIIA-IIA) Cr, W, Mo, Mn, Fe, Cu, Zn

Group 13 (III) Ga

Group 14 (IV) Sn, Pb

Group 15 (VII) Sb

These fractional distillation tubes have a number of simple and simple distillation functions. That is, fractionation is performed by packing the distillation tube with a high surface area material that backflows the liquid stream to ensure complete equilibrium between the liquid drop and the vapor rise. Only the partial condenser is installed in the fractional distillation pipe to produce the backflow and refined gas body HF and deliver it to the HF ion purifier (IP). The HF of this stage is refined in a conventional standard manner, with the possible overturning of the arsenic treatment chemistry or the quenching necessary to remove such a chemical.

HF IP is used as an additional purity assurance measure before injecting HF gas into the feeder system. These elements may be present in the treatment solution or injected into the IP to absorb the sulfate that is delivered to the HF stream. The IP test showed a significant reduction in HF gas stream contaminants for the following elements:

Group 2 (II) Sr, Ba

Group 6-12 (VIA-IIA) Cr, W, Cu

Group 13 (III) B

Group 14 (IV) Pb, Sn

Group 15 (V) Sb

The majority of these elements are useful for addressing As pollutant inhibition. The transfer to the fractionation distillation tube resulting from the excess of contaminants in As treatment can be rectified at this stage.

Production of buffered HF

3A shows a schematic of a process flow in a generation unit producing ultra-pure ammonia into hydrofluoric acid to produce buffered HF, and FIGS. 3B1 to 3B3 show PID drawings of samples implementing the process flow of FIG. 3A In detail.

An important feature of the present invention is that the dissolution of certain metal impurities (e.g., Fe, Ni) from the vapor stream is slower than the dissolution of HF. When a two stage process is used and some impurities are dissolved in the first scrubber, the second scrubber operates in a saturated state of about 105%, so that such light impurities sink to the top of the distillation column. Therefore, the second scrubber produces high purity hydrofluoric acid.

In a preferred embodiment of the present invention, the liquid volume of the ammonia purifier is 10 L and the maximum gas outlet rate is about 10 L / min. The cleaning liquid is continuously or incrementally refined sufficiently at least once in 24 hours.

The product concentration (at both developmental stages) was measured using a sonometer for concentration measurement (from Mesa Labs), but may optionally be measured using conductivity, density, refractive index or IR spectroscopy.

To begin the process, the total concentration of HF and NH ₃ dissolved in water should be determined. For example, 40% by weight of ammonia in 1 kg, i.e., a fluorinated solution, is 400 g of NH ₄ F and 600 g of ultra pure water. Since the molar ratio of HF to NH ₃ is 1: 1 in NH ₄ F purification, 400 g of NH ₄ F contains 216 g of anhydrous HF and 184 g of anhydrous NH ₃ (MW NH ₄ F237, MW HF = 20, MW NH ₃ -17).

Upon completion of the HF formation cycle, 216 g of HF are dissolved in 600 g of water or 26.5 wt% of water. The on-board instrument is sent to add HF to the product concentration. Optionally, 49% HF can be diluted to this concentration.

26.5% HF solution is formed with 189 g of NH ₃ added to form a 40% NH ₄ F solution.

Other concentrations and molar ratios can be set by the concentration mechanism, and for different applications, by adjusting the concentration mechanism.

Wafer cleaning

Several cleaning stations in a conventional semiconductor manufacturing line are shown in FIG. The first unit in the cleaning line is a resist removal station 41 which is applied to the semiconductor surface by the combination of aqueous hydrogen peroxide 42 and sulfuric acid 43 to strip the resist. The resist removal station proceeds to a rinse station 44 that applies deionized water for rinsing the removal solution. The on-site downstream stream of the rinse station 44 becomes the wash station 45 where ammonia and aqueous hydrogen peroxide solution are applied. This solution is supplied in one of two ways. First, the mixture 47, which is obtained by combining the aqueous ammonia 31 and the aqueous hydrogen peroxide 46, is supplied to the washing station 45. Secondly, a hydrogen peroxide aqueous solution 48 in which pure gaseous ammonia 32 is vaporized produces a similar mixture 49, which is likewise supplied to the washing station 45. Semiconductors, once washed with ammonia / hydrogen peroxide conjugate, are sent to a second rinse station 50 which applies deionized water to remove the wash solution. The next station is an additional cleaning station 54 that additionally cleans by adding an aqueous solution of hydrochloric acid (55) and hydrogen peroxide (56) to the semiconductor surface. This station is accompanied by a final rinse station 57 which removes HCl and H ₂ O ₂ by adding deionized water. The buffered HF diluted in the deglaze station 59 is applied to the wafer to remove the native oxide or other oxide film. The diluted buffer hydrofluoric acid is fed directly to the generator 70 via the sealed pipe. As described above, the reservoir 72 stores the anhydrous HF in which the stream of the gaseous body HF is supplied to the generator 70 via the ion purifier 71. The gaseous ammonia is supplied to the generator 70 in a bubbling state to produce a buffered solution, and ultrapure deionized water is added to obtain the desired diluent. These stations are subjected to rinsing in stationary deionized water (station 60) and dried in station 58. The wafer or wafer arrangement 61 is stored on the wafer support 52 and carried by a robot 63 or other conventional sequential processing means from one workstation to the next. Fully automatic, partially automatic or completely non-automatic transport means are all possible.

The system shown in Fig. 2 is merely an example of a cleaning line of a semiconductor facility. Typically, a cleaning line for high-precision manufacturing can be drastically changed from the one shown in FIG. 2 by removing or adding one or more units of the depicted unit or by replacing a unit not shown. However, the concept of on-site preparation of high purity aqueous ammonia in accordance with the present invention is applicable to all such systems.

It is well known in the art to use ammonia and hydrogen peroxide as semiconductor cleaning media for workstations such as the cleaning station 45 shown in FIG. While varying the ratios, the nominal system consists of deionized water, 29 wt% ammonium hydroxide and 30 wt% hydrogen peroxide in a volume ratio of 6: 1: 1. The detergent is used at the time of removing the organic residues, and the ultrasonic agitation at a frequency of about 1 MHz is carried out together to remove particles at an ultrafine size.

In one class of embodiments, the purification (or purification and generation) system is located close to the destination of the ultra-pure chemicals in the production line so as to move only a short travel distance between the purification unit and the production line. Alternatively, for a plant with multiple destinations, the ultra-pure chemicals from the refinery (refinery and generation) unit may be passed through intermediate storage tanks before reaching the destination and fed through individual outlets from the storage tanks to their respective destinations do. In either case, the ultra-pure chemical is directly applied to the semiconductor substrate without being packaged or transported and stored in a small inline reservoir, so that when the chemical is manufactured and produced for use outside the manufacturing facility, It does not come into contact with potential sources of contaminants. In this kind of embodiment, the distance between the purification system where the ultrapure chemical remains and the destination on the production line is typically a few meters or less. If the purification system is a central plant wide system consisting of pipe connections requiring two or more stations, the distance may be 2,000 feet or more. Substance that has not been injected with contaminants can be transported through ultra-clean transportation lines. In most applications, stainless steels or polymers such as high density polyethylene or fluorinated polymers can be used advantageously.

Since the purification unit is close to the production line, the water used in the unit can be refined according to semiconductor manufacturing standards. These standards are commonly used in the semiconductor industry and are well known to those skilled in the art and have been accumulated in industry studies and standards. Methods for purifying water in accordance with these standards include ion exchange and reverse osmosis. Ion exchange methods typically include a unit such as a chemical processor, such as a chlorination machine to kill organisms; Sand filters for particle removal; Activated charcoal filters to remove traces of chlorine and organic matter; Diatomaceous earth filter; Anion exchangers for removing ionized acids; A mixed bed grinder including both a cation and an anion to remove additional ions; A sterilizer such as a chlorine processor or an ultraviolet processor; And most or all of the filters that filter to 0.45 mu or less. The reverse osmosis process passes water under pressure through an optional permeable membrane that does not pass a large number of dissolved or suspended materials, instead of one or more units of the ion exchange process. A typical standard for purified water produced from such a process is that it has a resistivity at 25 캜 of at least about 15 megohm-cm (typically 18 megohm-cm at 25 캜), an electrolyte of less than about 25 ppb, a particulate content of less than about 150 / A microbial content of not more than about 10 / cm3, and a total organic carbon of not more than 100 ppb as the standard.

In the method and system of the present invention, high precision control of the concentration and outflow rate enhancement of the product can be accomplished by making accurate measurements and measurements using known equipment and instruments. Such control can be accomplished by convenient means by sonic speed sensing. Other methods have already been understood by those skilled in the art. If necessary, it is possible to implement variously modified density control loops that use conductivity instead of sound velocity.

Variations and Application Examples

As those skilled in the art will recognize, the innovative concepts described in the application of the present invention can be applied to a wide variety of modifications and variations, and thus the scope of the disclosed invention is not limited to the specific embodiments shown.

For example, as will be understood by those skilled in the art, the teachings of the present disclosure may be incorporated into semi-continuous or continuous on-site mixing methods of ultra-pure chemicals.

As another example, the disclosed innovations can be applied to the fabrication of discrete semiconductor devices such as optoelectronic devices and power devices, although not strictly limited to the manufacture of integrated circuits.

As another example, while the disclosed innovations may be applied to other manufacturing techniques to which integrated circuit manufacturing methods such as thin film magnetic heads and active matrix liquid crystal displays are applied, they are primarily applied to integrated circuit fabrication, do.

The ultra-pure chemical delivery route to the semiconductor front end includes an in-line or pressure reservoir. Thus, the expression "direct pipe connection" in the claims does not preclude the use of such storage, but excludes exposure to uncontrolled standby.

Further, the present invention is not limited to using only one sensor. For example, sonic sensing in the preferred embodiment of the present invention has the disadvantage that because of the high-helix HF solution (close to 1%), the sensor output does not have a one-to-one relationship in concentration. Therefore, the electrical conductivity measurement is preferably used to control the final dilution factor of HF to the highest dilution rate of the preferred embodiment of the present invention.

Claims (27)

A method for precisely generating an ultra pure liquid chemical from an on-site semiconductor process facility, Controllably supplying first, second, and third ultrasound reagent components from the first, second, and third sources; Mixing the first and second ultrapure reagent components to produce a first ultra pure product mixture with a first precisely selected product under control of the output of the sensor providing a one dimensional measurement; Mixing the first ultra pure compound and the third ultra pure reagent component under control according to the output of a sensor providing a one dimensional measurement to generate from a second ultra pure compound having a second precisely selected product ; Providing the second ultra-pure mixture to a pipe connection that delivers the aqueous solution to the root to a destination in the semiconductor device fabrication facility. The method of claim 1, wherein the first and second reagent components are all acids. 2. The method of claim 1, wherein the two mixing operations are automatically controlled in a closed loop connection. 2. The method of claim 1, wherein the two mixing operations are automatically controlled in a relationship that includes a feedforward relationship. The method of claim 1, wherein the at least one sensor is a sonic sensor. CLAIMS 1. A method for generating an accurate formula of an ultra-pure liquid chemical agent from a semiconductor process facility to on-site, Controllably supplying first, second, and third ultraclean reagent components from the first, second, and third sources; Mixing the first and second ultra-pure reagent components by generating a first ultra-pure compound at a first precision selection ratio under a control relationship according to the output of the first sensor; Mixing the first and second ultrapure reagent components to produce a first ultra pure product mixture with a first precisely selected product under control of the output of the sensor providing a one dimensional measurement; Unlike the first sensor, which provides a one-dimensional measurement, to generate from a second ultra-pure compound having a second precisely selected product, the first ultra-pure degree under the control relationship according to the output of the second sensor, Mixing the compound with the third ultrapure reagent component; Providing the second ultra-pure mixture to a pipe connection that delivers the aqueous solution to the root to a destination in the semiconductor device fabrication facility. 7. The method of claim 6, wherein the first and second reagent components are all acids. 7. The method of claim 6, wherein the two mixing operations are automatically controlled in a closed-loop relationship. 7. The method of claim 6, wherein the two mixing operations are automatically controlled in a relationship that includes a feedforward relationship. 7. The method of claim 6, wherein the at least one sensor is a sonic sensor. 7. The method of claim 6, wherein the one sensor is a sonic sensor and the other sensor is a conductivity measurement. A method of mixing one or more fluids, Providing at least a first fluid and a second fluid to be mixed; Flowing fluid through a means for mixing the fluids to form a mixed fluid; Sending ultrasound through the mixed fluid; Measuring the velocity of the sound wave through the mixed fluid to indirectly measure the ratio of the first fluid volume to the second fluid volume in the mixed fluid to indicate the density of the mixed fluid. 13. The method of claim 12, wherein the first fluid is acid. 13. The method of claim 12, wherein the second fluid is acid. 13. The method of claim 12, wherein the first and second fluids are both acid. In an on-site system of a semiconductor device manufacturing facility that provides ultra-pure reagents to a semiconductor manufacturing process, A first, a second, and a third source coupled to supply first, second, and third ultrapure reagent components to the semiconductor process; A mixing device coupled to the source to receive the ultrapure reagent component and to generate the mixture; A sensor for monitoring the composition of the mixture component generated by said mixing device; The introduction of the reagent component into the mixing device in which the first and second components are first mixed at a precisely selected rate and the second and third components are mixed at a second accurately selected rate, Said control logic being coupled to and configured to control said control logic. 17. The system of claim 16, wherein the first and second reagent components are all acids. 17. The system of claim 16, wherein the control logic has a feed forward relationship. 17. The system of claim 16, wherein the at least one sensor is a sonic sensor. In an on-site system of a semiconductor device manufacturing facility that provides ultra-pure reagents to a semiconductor manufacturing process, A first, a second, and a third source coupled to supply first, second, and third ultrapure reagent components to the semiconductor process; A mixing device coupled to the source to receive the ultrapure reagent component and to generate the mixture; A sensor for monitoring the composition of the mixture component generated by said mixing device; The first and second components are first mixed in a precisely selected ratio according to the output of the first one-dimensional sensor, and the second and third components are accurately and secondly mixed in accordance with the output of the second one- And a control logic coupled and configured to control the introduction of the reagent component into the mixing device mixing at a selected rate. 21. The method of claim 20, wherein the first and second reagent components are all acids. 21. The method of claim 20, wherein the control logic comprises a feedforward relationship. 21. The method of claim 20, wherein the at least one sensor is a sonic sensor. In an ultra-pure fluid mixing system, First and second chemical dispensers adapted to respectively receive the first and second fluids to be mixed; A process connection between a first distributor and a second distributor for mixing the first and second fluids to flow through the first and second chemical distributors and form a mixed fluid, To further flow the mixed fluid through the desired region; Is provided in an area sufficient to transmit ultrasonic waves through the mixed fluid and indirectly measures the rate defined by the amount of the first chemical in the mixed fluid versus the amount of the second chemical by measuring the speed of the sound waves through the mixed fluid Wherein the system comprises an ultrasonic radiation device. 25. The system of claim 24, wherein the first and second reagent components are all acids. 25. The system of claim 24, wherein the control logic comprises a feedforward relationship. 25. The system of claim 24, wherein the at least one sensor is a sonic sensor.